Slashdot videos: Now with more Slashdot!

View

Discuss

Share

We've improved Slashdot's video section; now you can view our video interviews, product close-ups and site visits with all the usual Slashdot options to comment, share, etc. No more walled garden! It's a work in progress -- we hope you'll check it out (Learn more about the recent updates).

bazzalunatic writes "The common golden orb web spider wards off ants from attacking it on its web by spinning an ant repellent (pyrrolidine alkaloid) into its silk. It could be used to develop a new insect repellent for humans. 'This study is among the first to show animals incorporating a chemical defence as a response to the threat of predation,' says Professor Mark Elgar of the University of Melbourne."

The key point here is that while the set of all mammals is not equivalent to the set of all animals, it is a subset thereof. So any true statement of the form "there exists a mammal such that X" remains true if you substitute "animal" for "mammal"

Also, you'd have to consider that Animal != Arachnid.
Which means that even if we accept your logic, the summary still isn't valid, since the researcher's spider would be no more valid than the GP's skunk.

Mine was among the first posts. Also, I am among the smartest individuals on the planet, and I am one of the only people who can write and compile a C program. In fact, my penis is among the largest, both in length and diameter, while still maintaining a comfortable size. My salary is among the top of any employee, ever, in the history of anything.

In short, I am among the top most amazing, handsome, perfect, richest people that ever walked the earth.

I agree - I was going to post pretty much the same thing. Chemical warfare is evident throughout biology from bacteria and yeasts all the way up through cephalopods to mammals like the skunk. Perhaps said researcher mis-spoke, or was referring to his particular field. Either way it proves that a specialist is a person who knows a great deal about very little.

Perhaps he's meaning this is one of the few cases of pro-active protection. Skunks, stink bugs, squids etc... use chemicals to defend themselves as a fire off at the last second defense, rather then a lace your home with it type of protection.

Oddly I read the summary as it being one of the first studies, more so than the first animal. I assume that not much study into the stinkbug or skunk was done because the reason for the repellent was clear. Is it possible that the spider's method is oderless to humans, thus making this interesting.

Is that spider a picky eater? Spiders will eat ants; I used to drop big black ants into spider webs as a child to watch the mayhem. Ants panic when they find themselves in the middle of a spider web, it's almost instinctual that they are in serious trouble. The spider wakes up and is like "WTF?" and will dart out and put some serious bites to it.

I don't know about fire ants though, they might be hard to eat, or they might be prime rib for spiders. Just as long as they get the first bite in on them, it's all good.

I think there is more to being "ant repellent" than a chemical, right?

A spider will eat one ant. It has trouble coping with thousands or even hundreds of thousands of ants at a time, however. I think the defense mechanism is to avoid the spider getting ambushed by a roving ant army, but any lone ants can be dealt with with the usual efficiency.

Ants zerging you in vast numbers are hard for any Earth life form to deal with, let alone a single spider setting in his web pondering WTF is with these Ants? A bunch of them will drag dead spiders back to the nest. We would destroy a large spider in the house and toss it out the front door on the sidewalk and ants would make off with it.

I have seen some big spiders in my days. One came walking into the kitchen one day in a country rental I was living in. Our dog walked up to it curious, it ran off like a s

That is a handy type of repellant, but will the Ants become immune to it after a while and hence wreck the Spiders? I would hope they do a chemical variant that is to a kilter enough in the composition that it warrants the spider's own webs to require these ants to evolve their own defenses against it.

I don't know. I suppose a trait that makes ants stay away from spider webs is more likely to keep an ant alive than kill one. Maybe it's more likely that the ants who stray into spider webs will be killed off instead of the ones who avoid them.

a trait that makes ants stay away from spider webs is more likely to keep an ant alive than kill one.

Interesting - you're suggesting that this "repellent" might not be so much a chemical produced intentionally by the spider but rather that ants have somehow become sensitive to this chemical? That would mean that at some point in the past, the were a hell of a lot of these spiders around and their favorite meal was ant.

That is a handy type of repellant, but will the Ants become immune to it after a while

Why? That's the good thing about a repellent: it does not kill ants. So unless you have ants that can only survive by eating spiders, a repellent should not affect the evolution of the ants in any way. They will just move out of the way and find something else to scavenge. Now if you start guarding all their food-sources with this repellent and put evolutionary "pressure" (ie, overcoming this chemical puzzle means significant advantage and survival likelyhood compared to other ant colonies) you might see re

"'This study is among the first to show animals incorporating a chemical defence as a response to the threat of predation,' says Professor Mark Elgar of the University of Melbourne."

That sentence is absurd coming from a biologist... either it's a misquote, or this professor smoked some strong stuff... Biology is FULL of chemical defences as a response to the threat of predation, and chemical offences for that matter. They are common in the insect world, and practically universal in the plant and microbial worlds. In fact looking at Biology as a whole, the majority of what evolution does on a day-to-day basis is developing new chemical defences as a response to the threat of predation. Perhaps repellents are a little more unusual in the animal (as opposed to plant) world or less well studied, but hasn't he ever heard of i.e. skunks? By the time we narrow this sentence down to something that makes sense it's a big yawner: "This study is amongst the first to show animals incorporating a chemical repellent targeted at specific predators into secretions they use to build external structures (webs)." Hmmm.

Admittedly I can't find it.(My GoogleFu is weak today.) I know they lay their eggs at the end of long threads to protect them. I thought I read somewhere that the threads have a chemical repellent to keep ants away (Since you'd think one tiny ant would just climb down and get it) but I can't find anything on Google confirming that.